Sunscreen compositions for application to plants

ABSTRACT

A sunscreen composition for application for plants comprises Titanium Dioxide (TiO 2 ), Zinc Oxide (ZnO), Silicon Dioxide (SiO 2 ), a surfactant, wetting agent, dispersant (SWD) and water. The composition forms a suspension concentrate when combined that when diluted in water provides a solution that provides uniform coverage using convention spraying equipment. A method of protecting plants including turfgrass from ultraviolet radiation, heat stress and/or sunburn comprises combining TiO 2 , ZnO, SiO 2 , SWD and water to form a suspension concentrate. The suspension concentrate is then diluted in water and applied to an area in which sun protection is desired.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims the benefit of and is a continuation ofco-pending U.S. patent application Ser. No. 12/869,514, filed Aug. 26,2010, the subject matter of which is incorporated by reference herein inits entirety for all purposes.

FIELD OF THE INVENTION

The present invention relates to sunscreen compositions. Moreparticularly, the present invention relates to sunscreen compositionsapplicable to plants such as turfgrass.

BACKGROUND OF THE INVENTION

Plants are living organisms many of which rely on the sun to survive.Green plants capture the energy of sun and convert the sunlight intoenergy to sustain the plant through the process of photosynthesis.Plants have many uses including food, medicines and other non-foodproducts, as well as aesthetic uses such as lawns, turf, gardens and thelike. Plant species are cultivated to provide shade, modifytemperatures, reduce wind and noise, provide privacy and prevent soilerosion. Lawn grasses, shade trees, ornamental trees, shrubs, vines,herbs, perennials and bedding plants are frequently used to beautifyoutdoor gardens. Sports such as football, soccer, baseball and golf areperformed on grass surfaces.

The effects of harmful radiation from the sun are well known. Exposureto ultra-violet (UV) radiation can damage the skin and deterioratecertain materials through extended exposure to sunlight containing theUV spectrum. In the case of skin, the protective layer of skin may burnor blister, causing painful and possibly irreversible damage. In extremecases of prolonged exposure, permanent damage such as skin cancer maydevelop. Sunscreens have been developed to help mitigate the damagesfrom UV radiation. Sunscreens may take the form of lotions, gels, oilsamong other formulae that may be applied to the skin and reflect orabsorb light in the UV spectrum, thus preventing the UV radiation frompenetrating the skin. Plants and other forms of life are alsosusceptible to the harmful effects of the sun. In particular, plants areadversely affected by the UV radiation emitted by the sun, as well asthe heat generated from the sun's radiation.

The ultra-violet spectrum (wavelength of 100-400 nanometers (nm)) iscomprised of UV-C (100-200 nm), UV-B (280-313 nm) and UV-A (315-400 nm)radiation. UV-B radiation in particular may have significantphoto-biological effects, causing modifications to the biological andbiochemical environment of the plant. Radiation may affect a plant bydirect destruction of the DNA at a molecular level, disruption of cellmembranes or other cell structures, and may inhibit variousphysiological functions, for example, photosynthesis, nutrientassimilation and chlorophyll and protein synthesis which may result inreduced growth and development of the plant.

An example where the damage of UV radiation to plants is acutely evidentis with regard to cultivated turfgrass. Cultivated turfgrass may be usedin locations such as golf courses, ball fields, parks and botanicalgardens. Over the area of the typical golf course, for example,different grass heights are maintained for different types of play andleisure activities. In some areas, for example, putting greens, it isdesirable to have a ball move rapidly across the surface during play. Toachieve this, turfgrass on greens may be maintained at blade lengths of⅛ inch (in.) or less. With such small blade lengths, the effects of heatand radiation are magnified and require measures be taken to preventdamage or possibly death of the turfgrass.

Golf courses and other institutional users of turfgrass must supplywater to the affected turfgrass in an amount sufficient to provideadequate cooling. This however, requires significant manpower and waterresources. In many areas, water resources are strictly monitored andrationed due to water shortages. This results in high costs for laborand irrigation and contributes to shortages of valuable water resources.It would be beneficial to have a composition to provide UV protectionfrom the sun and can be spread uniformly and over a wide area of theterrain.

SUMMARY OF THE INVENTION

A composition comprising titanium dioxide (TiO₂), zinc oxide (ZnO),silicon dioxide (SiO₂), a surfactant, wetting, dispersant agent (SWD)and a pigment are suspended in a suspension concentrate for use as sunprotection for plants, for example, turfgrass. A dilute solution usingthe composition is suitable for application using conventional sprayingequipment such as a backpack sprayer or a boom sprayer. The TiO₂ andZnO, in combination form an aggregate composed of varying sizedparticles resulting in enhanced sun protective properties. The particlesare suspended in such a way that they are evenly dispersed throughoutthe composition and thus provide even coverage when sprayed. Thecomposition protects the plant through its high refractive index andattenuation of ultra violet radiation resulting in less plant damagefrom drought, heat stress, and sunburn.

DETAILED DESCRIPTION OF THE EMBODIMENTS

When used in this specification, the term exemplary should be given themeaning of representative or serving as an illustration or specimen. Useof the term exemplary should not be construed to indicate any otherstatus such as preferred, commendable, worthy of imitation, or the like.

By shielding a plant, for example, turfgrass from harmful ultra-violet(UV) radiation, the health and vitality of the plant may be dramaticallyimproved. The rate of photosynthesis in plants is directly affected bytemperature. For example, when turfgrass reaches a temperature of about84° F., the turfgrass plant shuts down, stopping photosynthesis untilthe temperature again drops into an acceptable range. Water in the soilis used by the plant in an attempt to regulate the leaf temperature.However, in situations where there is inadequate water available tocompensate for the high temperature, the plant goes dormant. Dormancy isobservable in browning of turfgrass and the cessation of growth. In thecontext of a household lawn, the turfgrass browns and remains that wayuntil the temperature drops, or sufficient water is applied throughwatering or rainfall at which time the turfgrass revives itself,becoming green and continuing to grow.

In turfgrass applications such as a golf course however, dormancy of theturfgrass creates additional problems. First, the aesthetics of brownturfgrass at a finely groomed golf course is unacceptable to mostcustomers utilizing the course. The additional pressure of pedestrianand cart traffic on the turfgrass contributes to further damage, as theturfgrass cannot grow and regenerate itself. Once the turfgrass isdamaged by traffic, it may not grow back, causing the permanent damageto be particularly evident. Common types of turfgrass used in golfcourses include but are not limited to Kentucky Bluegrass, Bentgrass,Ryegrass, Bermuda grass, Fescue and the like.

By way of non-limiting example, the composition may be used on ryegrass.Ryegrass is a popular choice for turfgrass because of its ability torapidly produce thick, durable turf. One of the world's most widely usedgrasses, Ryegrass possesses the ability to germinate in as little as 7to 10 days. Being a cool season grass, ryegrass is commonly used inNorthern regions, or is used to overseed dormant grass during the wintermonths in hotter regions, such as the Southern United States. Ryegrassproduces dark green turf with a strong root system and is resistant tosome diseases which frequently affect other grasses like bluegrass.Ryegrass thrives in a variety of soil types and even grows well in clayand compacted areas. When the composition is applied to the turf canopy(the distance between the soil and the tip of the blade of turfgrass) ofryegrass, the UV blocking properties of the composition protect theryegrass from sun damage and help produce healthy vibrant turfgrass.

Certain compositions have traditionally been used in an attempt toshield plants from the damaging effects of the sun. The main ingredientsof these conventional compositions have been calcium carbonate(limestone) or kaolin clay. These products act to create a thick filmover the plant or fruit to prevent insect damage (e.g. in the case ofkaolin clay) and sun damage. Compositions that use limestonepreparations are very high in pH. As a result, such compositions are notsuitable for turfgrass where high pH conditions are undesirable, in thatamong other things, high pH environments facilitate fungal diseases.Additionally, these materials are highly soluble in water, and tend towash off the plant surface when it rains. Furthermore, the film createdby kaolin clay applications is not suitable for turfgrass for aestheticreasons, as the clay changes the color of the turfgrass to the reddishbrown color of the clay.

An embodiment of the composition provides exceptional sun blockingcharacteristics when applied to the surfaces of plants, such asturfgrass. In an embodiment, the composition comprises the following:TiO₂, ZnO, SiO₂, a surfactant/wetting/dispersant agent (SWD), and apigment. Combined with a small amount of water, this produces asuspension concentrate. The suspension concentrate may be diluted inwater to be used for example, in a sprayer and applied to an affectedarea. The proportion of TiO₂ may be a range of about 15%-35% by weightcomposition with an exemplary proportion of about 27% by weight. Theproportion of ZnO may be in a range of 6%-17% by weight composition, inan embodiment about 9% by weight. In a exemplary embodiment, the ratioby weight composition of TiO₂ to ZnO is between about 3:1 to 5:1. Theproportion of SWD may be in the range of 15%-35% by weight compositionwith an exemplary proportion of about 27% by weight. SiO₂ is present ina proportion by weight composition in the range of 5%-25% with anexemplary proportion of about 18% by weight.

Due to the white color of the TiO₂ and the ZnO, a pigment with aproportion composition of about 6% by weight may be added. The amount ofpigment may be adapted so as to impart a color in the blue or green huesand produce a desired color of turfgrass upon application. For example,in an exemplary embodiment, the pigment may include a copper compound toimpart a blue-green hue. The remainder of the composition is water, forexample, in a proportion of about 9.5% by weight.

The properties of the individual components are described herein.

Titanium dioxide (TiO₂) occurs in nature, most commonly in a form knownas rutile, a very stable form of TiO₂. Rutile has one of the highestrefractive indices of any known material. A high refractive indexattenuates UV radiation from the sun, redirecting the radiation as itpasses through the TiO₂. TiO₂ has strong UV absorbing capabilities thatalong with its high refractive index provide very high UV protection.Additionally, TiO₂ is also stable and not subject to discoloration underUV light. Further, TiO₂ is a photo-catalyst under UV light. When exposedto UV light, valence electrons in the TiO₂ are released causing surfaceoxidation which serves to eliminate potentially harmful organicsubstances such as bacteria and fungi. The anti-microbialcharacteristics of TiO₂ as a photo catalyst may protect turfgrass fromharmful bacterial or fungal infections in addition to its sun blockingproperties.

Zinc oxide (ZnO), like TiO₂ has a high refractive index and alsoexhibits anti-bacterial properties. ZnO in the presence of waterproduces Hydrogen Peroxide when exposed to UV light. Both ZnO and TiO₂are opaque and white in color and often used as white pigments.Therefore, according to an embodiment, the composition includes apigment to compensate for the opacity of the TiO₂ and the ZnO. Theparticle size of ZnO affects the wavelength at which absorptioncharacteristics are maximized. Thus, the use of a variety of particlesizes in an aggregate form and the tandem use of TiO₂ and ZnO providebroad protection across the entire UV spectrum.

Silicon dioxide (SiO₂) promotes plant health through the formation of athick silicated epidermal cell layer that maintains erect leaves andenhances photosynthesis. SiO₂, also known as silica, is the mostabundant mineral in the Earth's crust. Silica is absorbed into theplant's epidemic layer and promotes resistance to pests through theformation of a thick cuticle silicon layer. Silica helps reduce waterlosses to transpiration and thereby increases the plant's ability toregulate its temperature.

As described above, TiO₂ has high opacity and a white color. ZnO isslightly less opaque than TiO₂ but still is characterized by a whitecolor. For this reason, application of TiO₂ and ZnO to plants, forexample, turfgrass leaves the plants with a white appearance. A pigmentis added to the composition so that application of the composition tothe plant, for example, turfgrass provides the plant with a naturalcolor appearance. In one embodiment, the pigment is generally blue withsome green pigments and is obtained copper compounds.

In order to get the particles of SiO₂, ZnO, and SiO₂ to remain insuspension, a surfactant, wetting agent and dispersant (SWD) is used. Asurfactant or wetting agent is a substance that lowers the surfacetension of a liquid and lowers the interfacial tension between twodifferent liquids. A SWD is utilized as part of the composition so theparticles of TiO₂, ZnO, and SiO₂ form a suspended solution preventingsedimentation and clumping. A surfactant allows the bonding of anon-aqueous substance like ZnO to be combined in solution therebyfacilitating even spreading and stable suspension in solution. Adispersant or dispersing agent is added to a solution to improve theseparation of particles and to prevent settling and clumping. By way ofa non-limiting example, AU-330L, manufactured by Adjuvants Unlimited ofTulsa, Okla. may be used as a SWD.

The TiO₂, ZnO, and SiO₂ begin as granules with particle sizes, forexample, in the range of about 0.5 to 1 mm. Smaller particles createdust while mixing and tend to reduce the operational lifetime ofspraying equipment and risk the health of operators who must handle thematerials and may breathe in dust from the dry raw materials. The use ofgranules reduces the dust created during the mixing process and producesthe aggregate of particle sizes that provide the widest range of UVprotection. The SWD maintains the aggregate particles in solution whichkeeps them sufficiently mixed for effective application to theturfgrass. If sedimentation or clumping occurs, the resultingcomposition does not fit through a nozzle in a sprayer. Therefore, it isimportant to maintain the particles in a solution. Such clumping, maycause non-uniform flow through the nozzle of a sprayer, resulting inuneven application to the turfgrass. In more severe circumstances,clumping may result in a fouled or clogged nozzle, further reducing theequipment's operational capacity and overall lifetime.

The sunscreen composition described herein is effective at improving thehealth and vitality of turfgrass exposed to heat stress and overexposureto the sun's UV radiation. Due to its consistency, the composition isdispersed uniformly via conventional spraying equipment and provideseven protection over the spraying area and provides the synergisticadvantageous properties provided by all the ingredients. When testsprayed on areas of turfgrass during times of extreme heat and sunlight,turfgrass covered with the composition exhibited vibrant healthy grasscompared to control areas that were not treated with the composition.

In an embodiment of the sunscreen composition, a suspension concentrateis formed consisting of TiO₂, ZnO, SiO₂, a pigment, water, and a SWD.The TiO₂ is added in a proportion of about 30.12 percent by weight. TheZnO is added in a proportion of about 9.04 percent by weight. SiO₂ isadded in a proportion of about 18.07 percent by weight. A pigment isadded to adapt the sunscreen composition to the color of the turf to betreated such that the pigment makes up a proportion of the sunscreencomposition at about 6.02 percent by weight. A SWD is added to form aproportion of about 27.10 percent by weight. Finally, water is added ina proportion of about 9.65 percent by weight. According to thisembodiment, an amount of suspension concentrate sufficient to cover oneacre may be prepared by combining 0.80 pounds (lbs) of water, 2.25 lbsof SWD, 2.50 lbs of TiO₂, 0.75 lbs of ZnO, 1.50 pounds of SiO₂ and 0.5lbs of pigment.

The suspension concentrate is diluted in water to form a sunscreensolution. The sunscreen solution may then be applied to an areacontaining plants to be protected in a conventional manner such as asprayer. The sunscreen solution when sprayed provides an even dispersionof particles providing effective protection from heat stress andsunburn.

In accordance with an embodiment of the composition, a sunscreen forapplication to plants including turfgrass, is formed by combining in dryform, TiO₂ in an amount representing from about 10% to about 45% byweight of the composition. The TiO₂ may be comprised of particles havingparticle sizes of about 0.5 millimeters (mm) to about 1.0 mm. ZnO isadded to the TiO₂ in a dry form such that the ZnO make up about 6% toabout 17% of the composition by weight. The ZnO may likewise becomprised of particles with particle sizes of about 0.5 millimeters (mm)to about 1.0 mm. In an exemplary embodiment, the ratio of TiO₂ to ZnO inthe composition by weight is about 3:1 to about 5:1. Added to thecombined dry TiO₂ and the dry ZnO, SiO₂ is added in a dry form such thatthe SiO₂ comprises from about 10% to about 30% of the composition byweight. The combined TiO₂, ZnO, and SiO₂ are then mixed with a SWD. TheSWD is a liquid, for example, AU-330L, a SWD manufactured by AdjuvantsUnlimited of Tulsa Okla. may be used as the SWD according to anembodiment of the composition. The SWD may constitute from about 15% toabout 35% of the composition by weight. The dry TiO₂, ZnO and SiO₂ alongwith the SWD are combined with water at a percentage by weight of about9% of the composition. The TiO₂, ZnO, SiO₂, SWD and water may further becombined with a pigment adapted to match a natural color of theturfgrass to which it is applied. A pigment added to the composition maymake up about 6% of the composition by weight. The combined componentsare then mixed in accordance with chemical mixing techniques well knownin the art. The resultant composition is a suspension concentrate. Thesuspension concentrate may be mixed with an amount of water to produce asunscreen solution adapted to provide UV protection from the sun and bespread uniformly and over a wide area of the terrain.

The sunscreen solution may then be applied to a plant, such as turfgrassby methods commonly employed in the art, such as convention high-volumehydraulic sprayer, low volume sprayers, ultra-low volume sprays,pressurized liquid injection and like. The relative amounts applied toturfgrass such as ryegrass, is about 1.7 ounces (oz.) to about 3.4 oz.per 1,000 sq. ft. In an embodiment, the first application of thecomposition may be performed prior to the onset of heat or sun stress orwhen the temperature exceeds 80° F. The composition may be applied every7 to 21 days depending on the rate used, existing weather conditions andthe growth rate of the turfgrass. A lower application interval may beused when conditions of low humidity and intense sun are forecasted. Itis desirable to provide continuous and uniform coverage is maintained toimprove the health of treated turfgrass. Tests performed on areastreated with the composition of this embodiment show increased growthrate and vitality of the treated turfgrass. Other benefits aredocumented based on the use of an embodiment of the composition. In atest on mature creeping bentgrass with a fairway height stand,compositions containing Titanium, Zinc and an embodiment of thecomposition were applied to test plots of bentgrass along with testplots treated with the commercial fungicide DACONIL brand ofchlorothalomil and compared to an untreated control to observe theeffect of the treatments on Dollar Spot, a fungal disease that affectsmany varieties of turfgrasses infected by the fungus Sclerotiniahomeocarpa. Test plots were rated as to Dollar Spot severity, turfgrasscolor and overall turfgrass quality. The test was conducted at a timewhen dollar spot pressure was severe and the level of turfgrass qualitywas low due to Dollar Spot blighting. Dollar Spot severity was reducedin all treatments compared with the untreated control. The commercialfungicide resulted in the highest turfgrass quality rating followed byan embodiment of the composition which performed better than either theTi or Zn alone. Testing thus shows that in addition to the sun screeningcharacteristics of the composition, the additional benefit of fungaldisease control is provided by the composition.

In testing, an embodiment of the composition consisting of TiO₂ in aproportion of about 30.12 percent by weight, ZnO in a proportion ofabout 9.04 percent by weight, SiO₂ in a proportion of about 18.07percent by weight, a pigment in a proportion of about 6.02 percent byweight, a SWD in a proportion of about 27.10 percent by weight, andwater in a proportion of about 9.65 was applied to five 5 cm×5 cm polymethyl methacrylate (PMMA) plates. An additional 5 cm×5 cm PMMA platewas left untreated. Each plate was placed over an integrating sphereaperture of a double monochromator spectroradiometer and irradiated witha solar simulator. The spectral irradiance at wavelengths from 250-800nm was measured at 1 nm intervals for each plate treated with thecomposition as well as the untreated plate. A transmission, T_(λ) of thecomposition at each wavelength was computed as the ratio of spectralirradiance transmitted by each substrate, with and without theembodiment of the composition. An average value of 1−T_(λ) for each testtreatment was computed as the percentage screened. Based on the test,the composition screened 76% of the solar energy in the ultravioletspectrum relative to the untreated plate. Furthermore, the compositionscreened 82% of visible solar energy and 14% of near infrared solarenergy.

The above provides a detailed description of a sunscreen compositionaccording to various embodiments of the described composition. Thisdescription is provided by way of example only and is not intended to belimiting in any way. The scope of the present invention is limited onlyby the accompanying set of claims.

What is claimed is:
 1. A sunscreen composition to be used on plantsconsisting essentially of: titanium dioxide (TiO₂); zinc oxide (ZnO);and a surfactant, wetting agent dispersant (SWD); and optionally one ormore of a pigment, water and silicon dioxide (SiO₂), wherein the TiO₂ isin an amount of about 15% to about 45% by weight and the composition iseffective in protecting plants from ultraviolet radiation damage.
 2. Thesunscreen composition of claim 1, wherein the ratio of TiO₂ to ZnO isfrom about 3:1 to about 5:1 by weight.
 3. The sunscreen composition ofclaim 1, wherein said pigment is in the composition.
 4. The sunscreencomposition of claim 3, wherein the pigment is adapted to match anatural color of the plants.
 5. The sunscreen composition of claim 3,wherein said pigment is a copper compound.
 6. The sunscreen compositionof claim 1, wherein the ZnO is from about 6% to about 17% by weight. 7.The sunscreen composition of claim 1, wherein the SWD is from about 15%to about 35% by weight.
 8. The sunscreen composition of claim 3, whereinsaid water is in said composition.
 9. The sunscreen composition of claim8, wherein the pigment is about 6% by weight.
 10. The sunscreencomposition of claim 1, wherein said TiO₂ and said ZnO combine to forman aggregate having a plurality of particle sizes.
 11. The sunscreencomposition of claim 1, wherein the TiO₂ is about 30.12% by weight. 12.The sunscreen composition of claim 1, wherein the ZnO is about 9.04% byweight.
 13. The sunscreen composition of claim 2, wherein the SWD isabout 27.10% by weight.
 14. The sunscreen composition of claim 8,including said SiO₂ in said composition.
 15. The sunscreen compositionof claim 14, wherein said SiO₂ is in said composition in an amount ofabout 18% by weight.
 16. The sunscreen composition of claim 1, whereinsaid water is in said composition in an amount of about 10% by weight.17. The sunscreen composition of claim 8, wherein said water is in saidcomposition in an amount of about 10% by weight.
 18. The sunscreencomposition of claim 1, wherein said TiO₂ is in amount from about 15% toabout 35% by weight.
 19. A method of protecting turfgrass from heatstress, sunburn or ultraviolet radiation comprising the steps of:diluting a concentrated sunscreen composition consisting essentially of:water; titanium dioxide (TiO₂) from about 15% to about 45% titaniumdioxide (TiO₂) by weight; zinc oxide (ZnO); a surfactant, wetting agent,dispersant (SWD); and optionally a pigment and/or silicon dioxide(SiO₂); and applying said diluted sunscreen composition on an area ofturfgrass in an amount sufficient to cover the turf canopy to therebyprotect the applied area of turfgrass from heat stress, sunburn orultraviolet radiation damage.
 20. The method of claim 19, wherein saidpigment is adapted to match a natural color of the area of turfgrass andsaid pigment is in an amount of about 6% by weight.
 21. The method ofclaim 19, wherein said TiO₂ and said ZnO combine to form an aggregatehaving a plurality of particle sizes.
 22. The method of claim 19,wherein the diluting is performed by mixing the concentrated sunscreencomposition with an equal part water.
 23. The method of claim 22,wherein, the TiO₂, and ZnO, are comprised of granules having sizes ofabout 0.5 millimeters (mm) to about 1.0 mm prior to said mixing step.24. The method of claim 19, wherein the concentrated sunscreencomposition consists essentially of: from about 10% said water byweight; from about 15% to about 45% titanium dioxide (TiO₂) by weight;from about 6% to about 17% zinc oxide (ZnO) by weight; and from about15% to about 35% surfactant, wetting agent, dispersant (SWD) by weight.25. The method of claim 19 wherein said TiO₂ is in an amount from about15% to about 35% by weight.